The recovery of cobalt from various process streams can conveniently be carried out by first precipitating the cobalt as a hydrated oxide and thereafter redissolving to produce an electrolyte from which cobalt can be electrowon. Where, as is common, the process stream contains significant amounts of other metals, most notably nickel, significant upgrading of the relative amount of cobalt present is achievable by precipitating the cobalt under oxidative conditions which ensure the formation of its trivalent oxide hydrate, sometimes referred to as cobaltic hydroxide, CO(OH).sub.3. Such an oxidative precipitation is achieved if the process stream is treated with sodium hypochlorite or chlorine in the presence of a base.
While from an economic viewpoint the procedure of forming a cobaltic oxide hydrate with the aid of chlorine is attractive, an impediment to its commercial application stems from the fact that the resulting filter cake is contaminated with chloride ions. Two undesirable consequences flow from such entrained chloride which contaminates the electrolyte from which cobalt is to be electrowon. Firstly it necessitates the use of relatively expensive anodes for the electrowinning operation since the commonly used lead alloy anodes would corrode rapidly in a chloride-containing electrolyte. Moreover, electrowinning from chloride-containing electrolytes is accompanied by chlorine evolution which is environmentally objectionable and necessitates the use of more elaborate cells with means for containing and exhausting the atmosphere.